1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device, and a substrate processing apparatus, and more particularly to a method for manufacturing a semiconductor device that includes a step of forming a silicon film on a substrate, and a substrate processing apparatus having a controller that performs control so as to form a silicon film on a substrate.
2. Description of the Related Art
Silicon nitride films and the like have been conventionally formed on a semiconductor wafer by a CVD method. For example, a method for forming a silicon nitride film on a Si film is known by which HCD (hexachlorodisilane: Si2Cl6) and NH3 (ammonia) are supplied as reactive gases into a reaction chamber heated to and maintained at 500-800° C. (see, for example, Japanese Patent Application Laid-open No. 2002-334869).
Other known methods include a method of forming a non-doped Si film by using SiH4 (monosilane), Si2H6 (disilane), or the like as the reactive gas and a method of forming a P-doped (phosphorus-doped) Si film and B-doped (boron-doped) Si film by adding PH3 (phosphine) to SiH4 (monosilane) or Si2H6 in the reactive gas in order to cause diffusion of B (boron) or P (phosphorus) as impurity when a Si (silicon) film is formed by a low-pressure CVD method.
When a Si film is formed by a lower-pressure CVD method, an impurity doped Si film and a non-doped Si film are sometimes formed continuously as a laminated structure. For example, according to a typical film lamination sequence diagram of a P-doped Si film and a non-doped Si film shown in FIG. 17, a Si wafer is carried (loaded) into a reaction chamber, the temperature inside the reaction chamber is stabilized at 600° C., SiH4 and PH3 are supplied as reactive gases and a P-doped Si film is formed. Then, a non-doped Si film is formed continuously in the same reaction chamber at a temperature of 600° C.
However, a problem arising when such a film lamination sequence is realized is that the impurity is present not only in the doped Si film of the lower layer. Thus, the impurity also diffuses into the non-doped Si film of the upper layer, thereby creating a broad concentration distribution (concentration profile) of the impurity in the non-doped Si film.
It is an object of the present invention to provide a method for manufacturing a semiconductor device that includes a step of forming a silicon film on a substrate, and a substrate processing apparatus having a controller that performs control so as to form a silicon film on a substrate.
One aspect of the present invention relates to a method for manufacturing a semiconductor device, comprising the steps of: loading a substrate into a reaction chamber; supplying reactive gases into the reaction chamber and processing the substrate; and unloading the processed substrate from the reaction chamber, wherein the step of processing the substrate includes: a first film formation step of setting the substrate to a first temperature and forming a first silicon film including impurity atoms on the substrate and a second film formation step of setting the substrate to a second temperature, which is lower than the first temperature, and forming on the substrate a second silicon film that includes no impurity atoms or has an impurity concentration lower than that of the first silicon film on at least the first silicon film.
According to the one aspect of the present invention, it is possible to provide a method for manufacturing a semiconductor device by which a sharp impurity profile can be obtained when a first silicon film including impurity atoms is formed on the substrate and then a second silicon film that includes no impurity atoms or has an impurity concentration lower than that of the first silicon film is formed.